The Amazon is the world's greatest rainforest. Will it survive in perpetuity? Those who study Amazon conservation fear one thing most of all: roads.

In wildernesses such as the Amazon, roads often open a Pandora's Box of environmental problems, such as illegal logging, colonization, hunting, and mining. A new study shows a great deal of illegal road building in the Amazon, with loggers and ranchers likely being key culprits.

Road to ruin... (photo by Rhett Butler)

A key finding of the study: For every kilometer of legal road in the Amazon, there are nearly three kilometers of illegal roads.